Hydrogen chloride dissolves in water, forming an acidic solution.
Name the experiment which demonstrates that hydrogen chloride is highly soluble in water.

Explanation

**Step-by-Step Solution:**

1. **Identify the Experiment:** The experiment that demonstrates the high solubility of hydrogen chloride (HCl) in water is known as the "Fountain Experiment."

2. **Setup of the Experiment:** In the fountain experiment, a dropper is used to introduce water into a flask that contains hydrogen chloride gas (HCl).

3. **Observation:** When the water is squeezed from the dropper into the flask, a red-colored fountain is observed. This red fountain indicates that the hydrogen chloride gas is dissolving in the water.

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